The present invention is related to light-weighted metal beverage cans and more particularly to an apparatus forming the base of such cans.
Light-weighted metal beverage cans and apparatus employed in forming the same are well known in the art. Typically, it is desirable to manufacture metal cans with as little material as possible to reduce the weight of the finished can, while maintaining the structural integrity of the same.
In typical can forming processes, metal stock is manipulated through various stages of a forming apparatus to form the shape and size of the finished can. One of the first steps taken in a can forming process is the placement of the metal stock into a cupping press wherein the metal stock is deformed into the shape of a cup. Next, the cup is conveyed to a wall ironing machine and the deformed metal stock is redrawn to start forming the general shape of the sidewall and base of the finished can. After the metal stock is redrawn, the metal stock is passed through one or more ironing stations wherein the metal stock is more finely and accurately manipulated into the final shape of the finished can. In one of the last forming steps, the metal stock is passed into a bottom forming station wherein the base of the metal can is formed into its final shape.
FIG. 1 shows a metal beverage can 10. The can sidewall and base have been formed in accordance with the method described above. The shape of the beverage can 10 is well known to those skilled in the art. Generally, the beverage can 10 has a circumferential sidewall 12 having an upper portion 14 and a lower portion 16. The upper portion 14 of the sidewall 12 is mechanically coupled with a tab end 18. The lower portion 16 of the sidewall is connected to the base 20.
FIGS. 2 and 3 show the base 20 in more detail. The base 20 includes a nose portion 22 upon which the beverage can rests when set upright. The nose portion 22 is connected with a relatively concave dome portion 24 by a gradually smooth transition. The nose portion 22 is also connected to the outer profile 26 by a gradually smooth transition. The outer profile 26 is connected to the lower portion 16 of the metal can sidewall 12 by a gradually smooth transition.
FIG. 4 shows a conventional bottom forming station 28 that may be employed to form the base 20 of the metal beverage can 10. The bottom forming station 28 comprises a ram 30 that is adapted to slide along a relatively horizontal plane from a first position (not shown) to a second position (as shown in FIG. 4). A punch sleeve 32 and a punch nose 34 are mechanically coupled with the ram 30.
The punch sleeve 32 and punch nose 34 are adapted to receive a partially formed metal stock 36. When the ram 30 is at the second position, the punch nose 34 forces the metal stock 36 into engagement with the bottom forming die 38 and ceramic insert 40 under a relatively high impact force, thereby, forming the final shape of the base of the metal can.
The punch sleeve 32 has an outer surface 42 that includes a relatively smooth upper portion 44 that conforms to the shape of the upper portion 14 of the circumferential sidewall 12 of the finished can 10. The outer surface 42 of the punch sleeve 32 also has a generally curved front portion 46 that conforms to the lower portion 16 of the circumferential sidewall 12 of the finished metal can 10. The outer surface 42 includes a lower portion 48 that defines a bore 49 and that is adapted to receive and abut with a portion of the punch nose 34, as described below. The punch sleeve may be made of a steel material, or a carbide material.
The punch nose 34 has an outer surface 52 that includes a protruding portion 54 that conforms to the nose portion 22 of the finished can 10. A relatively upwardly angled front portion 56 is connected to the protruding portion 54 by a gradually smooth transition and conforms to the outer profile 26 of the finished can 10. A downwardly angled back portion 58 is connected to the upwardly angled portion 56 at an apex 60 and is adapted to abut with the lower portion 48 of the punch sleeve 32. The remaining sections of the outer surface 52 of the punch nose 34 are adapted to be slip fit between the punch sleeve 32 and a retaining bolt 62 to maintain the punch nose 34 in an operating position.
The punch nose 34 may be made of a steel material, such as hardened tool steel-M2, or a ceramic material. Punch noses that are made of a steel material are typically coated with a chemical material, such as titanium nitride, for various reasons. One reason is that the chemical material provides a xe2x80x9cmobilexe2x80x9d surface that enables the metal stock to be drawn to form the base of the metal beverage can with a reduced metal thickness as the punch nose impacts the bottom forming die 38 and ceramic insert of the extractor 40.
In the operating position, the punch nose 34 is placed within the punch sleeve bore 49 such that the punch nose and punch sleeve are securely positioned adjacent one another with a relatively small diametrical clearance xe2x80x94.001 inches. Between punch nose 34 and punch sleeve 32 there is a gap at a location called a split line 64. This gap may measure about .001 inches. The split line 64 has a junction area 66, which is the entrance into the split line 64, proximate the apex 60 of the punch nose 34 and the end of the punch sleeve. In this arrangement, the outer surfaces of the punch sleeve 44 and 46, and punch nose 54 and 56 form the profile of the can body and base.
It is noted that the sections on the punch sleeve and punch nose that the metal stock is in actual contact with as the base is being formed are called xe2x80x9cactive locations.xe2x80x9d Those sections on the punch sleeve and punch nose that are not in contact with the metal stock as the base is being formed are called xe2x80x9cnon-active locations.xe2x80x9d As shown in FIG. 4, the junction area 66 is located along an active location.
Over time, the punch sleeve 32 and punch nose 34 may become misaligned along the junction area 66. As the metal stock is drawn over a misaligned junction area 66, stress lines may be formed in the base of the finished metal can. The area around a stress line is likely to corrode and then crack after the beverage can is filled with a liquid. It would, therefore, be desirable to provide an apparatus that reduces the likelihood of stress lines being formed in he base of a finished metal can.
Conventional methods of maintaining the punch nose 34 and punch sleeve 32 in a proper alignment require corresponding punch noses and punch sleeves to be manufactured within substantially tight tolerances. The manufacturing of punch noses and punch sleeves within these tight tolerances is relatively difficult and costly to obtain. It would, therefore, be desirable to provide a base forming apparatus that is relatively more efficient to manufacture.
The chemical coating that is applied over the outer surface of a steel punch nose is likely to crack and dislodge from the punch nose during the base forming operation. The dislodged chemical flakes are likely to accumulate along the junction area 66 and contact the metal stock 36 as the metal stock is drawn. Unfortunately, these chemical flakes scratch the metal stock as the base of the finished metal can is being formed. The area around these scratches is likely to corrode and then crack after the beverage can is filled with a liquid. It would, therefore, be desirable to provide an apparatus that reduces the likelihood of scratches being formed on the base of a metal beverage can.
A punch sleeve in a bottom forming station for forming a metal beverage can having a sidewall and base portion is provided. The punch sleeve comprises a body having a sidewall that defines a bore for securely receiving a punch nose. The sidewall has a first section that corresponds to the shape of at least a portion of a beverage can base. The sidewall has a second section that corresponds to at least a portion of a can sidewall. The second section is integrally coupled with the first section. The sidewall also has a third section that is adapted to communicate with a punch nose and form a slip line that has a junction area in a non-active area. The third section is integrally coupled with the first and second sections.
In another embodiment, a punch sleeve as described above, having a body made of carbide material, is provided.
A punch nose for a bottom forming station for forming a metal beverage can having a sidewall and a base portion is provided. The punch nose comprises a body having a sidewall which has a first section that corresponds to the shape of at least a portion of a beverage can base. The punch nose sidewall has a second section that is integrally coupled with the first section. The second section is adapted to communicate with a punch sleeve and form a slip line that has a junction area in a non-active area. The slip line has a close slip fit wherein there is no perceptible play radially between the punch nose and punch sleeve.
A punch nose as described above having a body made of a ceramic material, a carbide material, or a steel material with a coating is provided.
Yet another embodiment of a punch sleeve for a bottom forming station for forming a base of a metal beverage can that has a sidewall and base is provided. This punch sleeve comprises a body having a first open end and a second open end. The body has an outer surface, which is adapted to receive metal stock that is to be drawn into the finished metal beverage can. The outer surface has a first section that extends from the first open end of the body to a location proximate the second open end of the body. The first portion corresponds to a can sidewall profile. A second section is integrally coupled with the first section. The second section corresponds to the profile of the base portion of a metal can. An inner surface extends from the first opened end of the body to the second open end of the body. The inner surface is integrally coupled with the second section and defines a bore that extends from the first open end of the body towards the second open end of the body. The bore is adapted to mechanically couple with a ram and a punch nose for forming the base of a finished metal beverage can. The inner surface further has a relatively angled potion proximate the second open end. The angled surface is formed at an angle that is between 170 degrees and about 180 degrees relative to the outer portion such that a slip line is formed with a junction area at a non-active location when the ram and punch nose are mechanically coupled within the recess.
A punch sleeve as described above, wherein the second section further includes a curved potion that corresponds to the outer profile of a metal can base for a metal beverage can is provided.
Yet another embodiment of a punch nose for a bottom forming station for forming the base of a metal beverage can is provided. This punch nose comprises a body portion having a sidewall that is adapted to be mechanically coupled with a punch sleeve by a retaining member. The sidewall has a support portion that is adapted to communicate with a retaining member to support the punch nose in an operating position. The base portion has a first and second end. A protruding portion that conforms to the nose portion of the base of a finished metal can is integrally connected to the support position. An upper surface is integrally connected to the protruding portion. The upper surface is adapted to communicate with a punch sleeve and form a slip line having a junction area in a non-active area.
A punch sleeve as described above, wherein the upper surface extends at a relative angle of about 30 to 45 degrees and is adapted to communicate with a punch nose to form a slip line with a junction area in a non-active area, is provided.
A bottom forming station for forming a metal can having a sidewall and a base portion is provided. The bottom forming station comprises a punch sleeve having a body. The body has a sidewall that defines a bore for securely receiving punch nose. The sidewall has a first section that corresponds to the shape of at least a portion of a beverage can base. The sidewall also has a second section that corresponds to at least a portion of a can sidewall. The second section is integrally coupled with the first section. The sidewall also has a third section that is adapted to communicate with a punch nose and form a slip line that has junction area in a non-active area. The third section is integrally coupled with the first and second sections.
The bottom forming station further comprises a punch nose. The punch nose comprises a body having a sidewall. The sidewall has a first section that corresponds to the shape of at least a portion of a beverage can base. The sidewall also has a second section integrally coupled with the first section, said punch nose adapted to be mechanically coupled within the bore of the punch sleeve with the second section of the punch nose in communication with the third section of the punch sleeve sidewall such that a slip line is formed with a junction area in a non-active area.
A bottom forming station as described just above, wherein the third section of the punch sleeve and the sidewall of the punch nose are at a relative angle of between about 170 degrees and about 180 degrees from horizontal, such that when in contact with one another a substantially horizontal slip line is formed with a junction area at a non-active location, is provided.